Buck Island Reef National Monument, or just Buck Island is a small, uninhabited, 176 acre (712,000 m²) island about 1.5 miles (2.4 km) north of the northeast coast of Saint Croix, U.S. Virgin Islands. It was first established as a protected area by the U.S. Government in 1948, with the intention of preserving “one of the finest marine gardens in the Caribbean Sea.” The U.S. National Monument was created in 1961 by John F. Kennedy and greatly expanded in 2001 by Bill Clinton, over the bitter opposition of local fishermen. Buck Island National Monument is one of few places in the Virgin Islands where endangered brown pelicans and threatened lest terns nest.

Buck Island Reef National Monument.

Most of the Monument area, which is administered by the National Park Service, is underwater and attracts around 50,000 visitors a year. With its 4,554-acre (18.43 km2) long reef there is plenty to explore and experience in the water. Snorkelers can follow an underwater marked trail on the eastern tip. It is one of only three underwater trails in the United States. Along the trail are plaques denoting information about marine flora and fauna commonly found in the area. Two thirds of the island is surrounded by an elkhorn coral barrier reef, providing an ecosystem for over 250 fish species and a variety of other marine life including spotted eagle rays, nurse sharks and lemon sharks, and juvenile Blacktip reef sharks and Whitetip reef sharks. In the spring endangered Leatherback turtles come onto the beach to nest while Green turtles and Hawksbill turtles nest during the summer months. Turtle Beach on the western edge of the island features a pristine white sand beach and has been voted one of the world's most beautiful beaches by National Geographic.

The National Park Service has been monitoring Buck Island for over 20 years. Most of the research is focused on fish, sea turtles, brown pelicans and least tern nesting. Natural disasters such as hurricanes, along with man-made problems such as ship groundings and oil spills, have negatively affected the ecosystem.[citation needed]Hurricane Hugo destroyed over 80% of beach forest, almost 100% of the south barrier reef was ruined, and most of the nesting areas for Green and Hawksbill turtles was eroded.